1. Field of the Invention
The present embodiments relate to a semiconductor device.
2. Background of the Related Art
An electric power converter device uses a semiconductor device configured as an intelligent power module (IPM) that contains a power semiconductor switching element and a control IC including a drive circuit for driving the power semiconductor switching element and a protection circuit in one package. An insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), or the like is used as the power semiconductor switching element.
The control IC includes the protection circuit that detects abnormality, such as chip overcurrent and chip overheat, of the power semiconductor switching element to protect the power semiconductor switching element and outputs an alarm to the outside from an alarm signal terminal of the package. When a chip of the power semiconductor switching element detects a predetermined electric current, temperature, or the like, the protection circuit stops operation of the power semiconductor switching element and protects the power semiconductor switching element from destruction due to abnormality, such as overcurrent and overheat.
This protection circuit stops the operation of the power semiconductor switching element when detecting that some sort of abnormality has occurred in the chip of the power semiconductor switching element, and thereby the power semiconductor switching element can be prevented from chip destruction. However, in a system configured with the electric power converter device including the IPM, sudden stop of the electric power converter device can stop the entire system.
In order to prevent this sudden system stop, there is a known technology in which a protection circuit has a function for predicting occurrence of abnormality in the IPM and eliminates factors that cause the abnormal stop of the IPM before the sudden system stop occurs (for example, refer to Japanese Patent No. 3635988). According to this technology, the protection circuit outputs a precaution of a precursory sign of abnormality, before detecting abnormality of the power semiconductor switching element and outputting an alarm of the abnormality. Hence, the protection circuit has a function for detecting abnormality of the power semiconductor switching element, and the IPM outputs a precaution to the outside.
However, in the technology of Japanese Patent No. 3635988, the precaution and the alarm are digital signals of certain pulse widths that differ from each other, in order to make it possible to output the precaution and the alarm from a common terminal. In this case, software of a microcomputer of a receiver side usually determines which signal a measured pulse width means, and thus there is a problem that the processing takes a certain amount of time and lacks instantaneousness.
Also, a semiconductor device that uses a plurality of power semiconductor switching elements is normally provided with as many protection circuits as the power semiconductor switching elements, and each protection circuit corresponds to one power semiconductor switching element. In this case, each of the protection circuits is configured as an individual semiconductor integrated circuit (IC), and a wired OR (alarm line) of alarm output terminals of all the protection circuits is connected to the outside in many cases in order to reduce the number of terminals and lines. In the past semiconductor device connected in this way, each protection circuit monitors the level of the alarm line, and if an alarm is issued from another protection circuit, stops the power semiconductor switching element corresponding to the protection circuit for the purpose of safety of the entire semiconductor device. However, if not only the alarm but also the precaution, which is needless to immediately stop the semiconductor device, is output from the same terminal at the same level (voltage) as the alarm, there is a problem that it is difficult for each protection circuit to operate appropriately.